[QuinnSjoblom]

I'm milling parts for rc helis out of 7075 aluminum. Some of them are very complex with hours of work so REALLY don't want to be snapping taps off in them. I imagine it's not that much of a challenge in aluminum vs harder stuff but I wanted to get some advice before I order taps. I've already done quite a bit just using regular cheap taps unguided by hand but I want to start using my cnc as a guide with a spring loaded center and handle (spindle doesn't reverse so only by hand). Mostly m3 threads, some m2.5, m4, m5. Mostly I'm just curious what is the right type of tap for the job that will be least likely to snap. Also what is the deal with bottom hole tapping? Some of my parts could be more efficient if I have that as an option but I don't know what's involved with bottom hole taps. More likely to snap? Harder to start? Do you start with a regular tap first, then get the bottom with a bottom tap? Any advice is greatly appreciated, mostly just need recommendations for the type of taps I want, willing to spend more than cheap Chinese stuff.

[ianagos]

I do rigid tapping on my machine with blind holes using polished spiral flute taps. I like balax,osg yg1. Look on eBay for them they are easy to find.

[ToolHIT]

In 7075 Aluminum a Cut Tap for Aluminum generally holds up well but if you really don't want to worry about breaking taps then I would recommend a Form Tap. In 7075 Aluminum, a Form Tap will give you a Better Quality Thread, Longer Tap Life and you won't have to worry about taps breaking in parts/chip evacuation. The only thing is you would need a different drill size for Form Taps. If you are ok with changing drill size then I'd go with a form tap, if not then a Cut Tap with a Higher Helix and extra room in the flutes for chip evacuation is the way to go.

A Bottoming tap has a 1.5-2 Thread Chamfer, a Modified Bottoming Tap has a 2-3 Thread Chamfer and a Plug Tap has a 4-5 Thread Chamfer. The longer the Chamfer or Lead the better a tap holds up and higher quality thread you will see. For Blind Holes a Spiral Flute Modified Bottoming Tap as it has a longer Chamfer or Lead which will give you much greater tap life as long as you have the clearance for the longer chamfer or lead. The Spiral Flute design will pull the chip out of the blind hole which allows you to tap a blind hole in 1 shot (a Spiral Flute Plug Tap is stronger with the Longer Lead but it will push the chips forward which doesn't work in blind holes unless you have the clearance).

In 7075 I've had a lot of luck with the YG Taps, here are the Spiral Flute Modified Bottoming Taps I'd Recommend:
M3 Spiral Flute Mod Bottoming Cut Tap
M4 Spiral Flute Mod Bottoming Cut Tap
M5 Spiral Flute Mod Bottoming Cut Tap
M2 Bottoming Roll Form Tap with Oil Groove
M3 Bottoming Roll Form Tap with Oil Groove
M4 Bottoming Roll Form Tap with Oil Groove
M5 Bottoming Roll Form Tap with Oil Groove

Hopefully this helps. Also, you can run a Roll Form Tap 1.5 to 2 times faster than a Cut Tap. If you need SFM info or anything else let me know

Mike

[QuinnSjoblom]

In 7075 Aluminum a Cut Tap for Aluminum generally holds up well but if you really don't want to worry about breaking taps then I would recommend a Form Tap. In 7075 Aluminum, a Form Tap will give you a Better Quality Thread, Longer Tap Life and you won't have to worry about taps breaking in parts/chip evacuation. The only thing is you would need a different drill size for Form Taps. If you are ok with changing drill size then I'd go with a form tap, if not then a Cut Tap with a Higher Helix and extra room in the flutes for chip evacuation is the way to go.

A Bottoming tap has a 1.5-2 Thread Chamfer, a Modified Bottoming Tap has a 2-3 Thread Chamfer and a Plug Tap has a 4-5 Thread Chamfer. The longer the Chamfer or Lead the better a tap holds up and higher quality thread you will see. For Blind Holes a Spiral Flute Modified Bottoming Tap as it has a longer Chamfer or Lead which will give you much greater tap life as long as you have the clearance for the longer chamfer or lead. The Spiral Flute design will pull the chip out of the blind hole which allows you to tap a blind hole in 1 shot (a Spiral Flute Plug Tap is stronger with the Longer Lead but it will push the chips forward which doesn't work in blind holes unless you have the clearance).

In 7075 I've had a lot of luck with the YG Taps, here are the Spiral Flute Modified Bottoming Taps I'd Recommend:
M3 Spiral Flute Mod Bottoming Cut Tap
M4 Spiral Flute Mod Bottoming Cut Tap
M5 Spiral Flute Mod Bottoming Cut Tap
M2 Bottoming Roll Form Tap with Oil Groove
M3 Bottoming Roll Form Tap with Oil Groove
M4 Bottoming Roll Form Tap with Oil Groove
M5 Bottoming Roll Form Tap with Oil Groove

Hopefully this helps. Also, you can run a Roll Form Tap 1.5 to 2 times faster than a Cut Tap. If you need SFM info or anything else let me know

Mike

Excellent. Great info! Thanks a lot. I will definitely look into form taps. I don't have much invested in drills yet so if form tapping can potentially give better quality threads and low risk for breaking, I'll definitely give it a shot. Thanks for the advice!

Looks like you don't have an m2.5 form, but I don't have many of those so ill just cut those few. The m3's are my main structural fasteners so a good strong thread will be nice. Sounds like form tap is the way to go for those.